PA28 LOST ELECTRICAL POWER IN INSTRUMENT CONDITIONS. FLT RETURNED TO VMC; AND BRIEFLY REESTABLISHED RADIO CONTACT FOR VECTORS THROUGH THE CLOUDS FOR AN APCH AND LNDG.

Narrative

THE SITUATION OCCURRED WHILST ON FINAL FOR THE GPS XX APCH. THE FIRST INDICATION OF ABNORMALITY OCCURRED SHORTLY BEFORE XING THE FAF WHEN THE GNS 530; MODE S XPONDER; AND HSI ABRUPTLY FAILED. APCH CTL ADVISED THAT ALT ENCODING WAS LOST. SECONDS LATER ALL ELECTRICAL PWR WAS LOST; RESULTING IN FAILURE OF THE GNS 430; TURN COORDINATOR; AND DIGITAL TACHOMETER. MY INSTRUCTOR ASSUMED CTL OF THE ACFT; IMMEDIATELY INITIATING A CLBING R TURN TO AN APPROX MAGNETIC HDG OF 270 DEGS AND AN ALT OF BTWN 4300-4700 FT MSL; OUR LAST KNOWN VFR ON TOP ALT. I THEN CONTACTED TRACON WITH A CELLULAR TELEPHONE AND APPRISED THE CTLR OF OUR PLIGHT BEFORE LOSING RECEPTION. MY INSTRUCTOR CONCURRENTLY DISCOVERED THE AMMETER INDICATED ZERO. AFTER EVALUATING THE SITUATION; WE DECIDED OUR BEST OPTION WAS TO HEAD TOWARD THE LAST KNOWN VFR CONDITIONS; THUS WE INITIATED A TURN TOWARDS A SE HDG. SHORTLY AFTER COMMENCING THE TURN; SUFFICIENT CHARGE ACCUMULATED TO OPERATE THE GNS 430 AND PERMIT RADIO COM. APCH THEN PROVIDED RADAR VECTORS THROUGH THE CLOUDS. WE BROKE OUT AT APPROX 900 FT MSL AND 1 SM FROM THE THRESHOLD AND LANDED WITHOUT INCIDENT. SUBSEQUENT PLT INSPECTION OF THE ACFT REVEALED THE ALTERNATOR BELT WAS MISSING. WE ESTIMATE THE BELT MUST HAVE BEEN LOST INSIDE CLASS B AIRSPACE.